Is there a branch of Sedevacanists that would not require a Catholic funeral?

My father passed away this week after a long illness. His faith would be described from a distance as a Sedevacanist which you would describe some of my siblings as as well. However up close I believe there to be quite a divergence in their beliefs. For example the church where my siblings pray, my father refused to even walk into it and has not attended any of his grandchildrens' Christenings or Confirmations. My father prayed by himself and had a altar in his room. I dont think he attended a Mass (apart from weddings, funerals) this century. Then the grave that he bought a few years ago is in a humanist graveyard - it's a field, there is no consecrated ground. His funeral wishes are a small service which he said could be at the funeral home, followed by prayers read by a friend as he is buried. My siblings have said that this is an absolute no to all of his wishes and that he has to have a Catholic funeral with Mass (probably at the church he refused to even step foot in) and buried in consecrated ground. They are saying because he received the last rites from their siblings' priest, that was his way at the end of ripping up his prior plans. So here is the question: **Is there a branch of Sedevacanists that would reject the need for the low Mass funeral and consecrated ground?** Was he dying with a clear conscience in regards to his funeral arrangements? I ask this as an agnostic who just wants to follow his father's wishes. Even though I don't believe them myself I want to respect his beliefs.